1. Field of the Invention
The present invention relates to a semiconductor photonic device, and more particularly to semiconductor photonic devices using III-V compounds such as GaN, InGaN, GaAlN, and InGaAlN.
2. Description of the Related Art
As materials for semiconductor photonic devices such as light emitting diodes (LEDs) and laser diodes (LDs) which emit blue light or ultraviolet light, or photo diodes which detect blue light or ultraviolet light, III-V compound semiconductors represented by the general formula InxGayAlzN (where x+y+z=1, 0xe2x89xa6x xe2x89xa61, 0xe2x89xa6yxe2x89xa61, and 0xe2x89xa6zxe2x89xa61) are known. The compound semiconductors have high light emission efficiency because they are of the direct transition type, and emission wavelengths can be controlled by the indium content, and thus these compound semiconductors have been regarded as promising materials for light emitting devices.
Since it is difficult to form a large single crystal of the InxGayAlzN, in order to form a crystal film thereof, a so-called xe2x80x9chetero-epitaxial growth methodxe2x80x9d is used, in which a crystal film is grown on a substrate of a different material, and generally, it is grown on a C-plane sapphire substrate. However, C-plane sapphire substrates are expensive, and moreover, because of large lattice mismatching, many crystal defects at dislocation densities of 108/cm2 to 1011/cm2 occur in grown crystals, and thus it is not possible to obtain quality crystal films having excellent crystallinity, which is a problem.
Consequently, in order to reduce lattice mismatching when InxGayAlzN is grown on a C-plane sapphire substrate and to obtain crystals having few defects, a method has been disclosed in which a polycrystalline or amorphous AlN buffer layer or a low temperature growth GaN buffer layer is provided on a C-plane sapphire substrate. For example, hexagonal GaN has a lattice constant in the a-axis direction (hereinafter referred to as xe2x80x9clattice constant axe2x80x9d) of 3.189 xc3x85, and AlN has a lattice constant a of 3.1113 xc3x85 which is close to that of GaN. In accordance with the above method, since lattice mismatching between the C-plane sapphire substrate and the buffer layer is reduced and at the same time lattice mismatching between the buffer layer and InxGayAlzN is reduced, a crystal film having few defects can be obtained. However, in this method, in addition to the expensive sapphire substrate, the structure becomes complex, resulting in a further increase in cost.
Additionally, an SiC substrate which has small lattice mismatching has been investigated. However, SiC substrates are much more expensive in comparison with C-plane sapphire substrates (approximately 10 times as costly as C-plane substrates), which is disadvantageous.
The present invention can solve the aforementioned technical problems associated with the conventional devices, provide a semiconductor photonic device having a high quality InxGayAlzN thin film on an inexpensive quartz substrate.
The semiconductor photonic device comprises: a Z-cut quartz substrate; and a compound semiconductor layer represented by InxGayAlzN (where x+y+z=1, 0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61, and 0xe2x89xa6z xe2x89xa61) and formed on the Z-cut quartz substrate. It is preferable that the [1000] direction, the [10{overscore (1)}0] direction, and the [11{overscore (2)}0] direction of the InxGayAlzN layer substantially correspond to the [1000] direction, the [10{overscore (1)}0] direction, and the [11{overscore (2)}0] direction of the quartz substrate, respectively. In addition, The semiconductor photonic device may further comprises a ZnO thin film or AlN thin film between the compound semiconductor layer and the Z-cut quartz substrate.
For the purpose of illustrating the invention, there is shown in the drawings several forms which are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown.